Problem: Simplify the following expression: ${-3r+7+8+2r}$
Explanation: Rewrite the expression to group the ${r}$ terms and numeric terms: $ {-3r + 2r} + {7 + 8}$ Combine the ${r}$ terms: $ {-r} + {7 + 8}$ Combine the numeric terms: $ {-r} + {15}$ The simplified expression is $-r+15$